Step 1: Prepare the Pan

Line an 8×8-inch baking dish with parchment paper, leaving overhang on the sides for easy removal. Set aside.

Step 2: Make the Base

In a large mixing bowl, combine the graham cracker crumbs, melted butter, and sweetened condensed milk. Stir until the mixture is fully moistened and thick.

Add the vanilla extract and mix again until evenly incorporated.

Step 3: Melt the White Chocolate

Place the white chocolate chips in a microwave-safe bowl. Microwave in 20-second intervals, stirring between each, until fully melted and smooth.

Pour the melted white chocolate into the crumb mixture and stir until completely combined.

Step 4: Add Mix-Ins

Gently fold in the mini marshmallows, festive sprinkles, and chopped pecans (if using). Mix just until evenly distributed.

Step 5: Press and Set

Transfer the mixture into the prepared pan. Use a spatula or the back of a spoon to press the mixture firmly and evenly into the pan, creating a smooth top.

Sprinkle a small amount of additional festive sprinkles over the top if desired for decoration.

Step 6: Chill

Refrigerate for at least 2 hours, or until completely firm and set.

Once chilled, lift the bars out using the parchment overhang and cut into thick squares.